This invention relates to a storage system which includes a hard disk drive and a storage controller, and more particularly, to a technology of processing an access request by the storage controller.
Representative access interfaces for a storage system include a fibre channel (FC), and Ethernet. The fibre channel and the Ethernet have become popular as elements for constituting a storage area network (SAN). The SAN constituted of the fibre channel may be called an FC-SAN, while the SAN constituted of the Ethernet may be called an IP-SAN.
For example, transfer efficiency of one physical port in the FC-SAN is 2.4 Gbps or the like. Transfer efficiency of one physical port in the IP-SAN is 1 Gbps, 10 Gbps, or the like.
An application executed by a host computer requests access of high throughput and high transaction to the storage system. Thus, one physical path cannot provide transfer efficiency required by the application. Hence, the host computer uses a plurality of physical paths to access the storage system. In this case, a multipath I/O, a link aggregation, or the like is used.
A technology of controlling a large storage system is disclosed in “Symmetric DMX Architecture Product Description Guide”, EMC Corporation, 2004. According to this technology, each physical port included in the storage system is controlled by one or two processors. The processor processes an access request received from a host computer through the physical port. Further, the processor controls data in a cache memory. In other words, many processors included in the storage system operate in parallel to control the entire storage system.
A conventional storage system includes a controller and a hard disk drive. The controller includes a SAN, a front-end interface unit, a processor, a cache memory, a memory, a back-end interface unit, and an internal network. The controller provides a storage area of the hard disk drive as a logical volume to a host computer.
The SAN is a network to interconnect the host computer and the storage system. The front-end interface unit includes a physical port connected to the SAN. A plurality of front-end interface units are included in the storage system.
The processor controls the front-end interface unit. The processor may be included inside or outside the front-end interface unit. The cache memory temporarily stores information containing an access request transmitted from the host computer.
The memory is used as a shared memory to store control information of the storage system. The back-end interface unit is connected to the hard disk drive. The internal network connects the components included in the controller to each other.
The front-end interface unit receives the access request from the host computer. Then, the processor processes the access request received by the front-end interface unit while referring to or updating the control information stored in the memory. Accordingly, the storage system can process the access request while maintaining consistency in processing and cache.